The goal of this project is to investigate the role of chromatin modifications and DMA methylation in activation or silencing of gene expression during initiation of lung development. Chromatin modifications and DNA methylation in conjunction with DNA binding factors regulate transcription to achieve cell specific gene expression. These mechanisms play a defined role in developmental programs, and have been shown to be involved in the establishment of the specific cell lineages that will give rise to various organs, including foregut derivatives such as the liver. Little is known about how these mechanisms influence gene expression in the developing lung. In a microarray analysis of the developing foregut carried during the previous period of this Program Project, we identified significant changes in the expression of genes associated with chromatin remodeling and DNA methylation, coincident with the formation of the lung primordium. The known important role of chromatin remodeling in cell fate decisions and differentiation led us to hypothesize that chromatin remodeling and DNA methylation play a regulatory role in initiation of lung development by establishing spatial and temporal patterns of gene expression in the embryonic foregut. Thus we propose to: 1) identify changes in epigenetic modifications of selected lung gene promoters during initiation of lung development in vivo and in cultured ES cells, 2) search for targets of activating chromatin remodeling complexes in embryonic lung cells, 3) analyze the function of chromatin remodeling genes and DNA methylation on the transcriptional activity of lung promoters in cells, and in wild type and genetically modified lungs. The proposed studies include the characterization of chromatin modifications of lung gene promoters by chromatin immunoprecipitation, DNA methylation and chromatin accessibility analyses in vitro and in vivo, a global analysis of new targets of epigenetic gene activation, and the functional evaluation of chromatin modification genes in lung gene development using foregut cultures and genetically modified mice. Our findings will increase the knowledge of how the early patterns of lung expression are regulated in vivo and in ES cells.